1. Field of the Invention
The invention relates to a switching current synthesis circuit, and more particularly to a switching current synthesis circuit for a power converter operating in a continuous current mode (CCM) and a discontinuous current mode (DCM).
2. Description of the Related Art
A power factor correction (PFC) power converter is a good example for illustrating the present invention. FIG. 1 shows a prior art of a PFC power converter. It includes a resistor 31 coupled to sense a switching current IL of an inductor 20. The resistor 31 is coupled in the charging and discharging path of the inductor 20. The current flowing through the resistor 31 is an average value of the switching current IL. Therefore, the circuit scheme shown in the FIG. 1 is called as “average-current control”. The drawback of the average-current control scheme has higher power consumption in the resistor 31. Furthermore, it cannot be applied to the parallel topologies for high efficiency power conversion, such as the solution shown in the prior art, such as U.S. Pat. No. 7,626,372 titled “Control circuit for multi-phase, multi-channels PFC power converter with variable switching frequency” and U.S. Pat. No. 7,944,721 titled “Switching control circuit for multi-channels and multi-phases power converter operated at continuous current mode”.